How did Robb get back to Riverrun from the Westerlands? The Lannisters found out about the secret goat track.

Who’s going to stop him, exactly? Stafford Lannister’s army is destroyed, Damon’s holed up in the Rock, and Forley Prester only has the garrison of the Golden Tooth, since he sent the 4,000 men he saved at the Camps to Oxcross.